1. Field of the Invention
The present invention relates to a device for detecting the compression of liquid refrigerant in a compressor when the compressor is started and a device for controlling the compressor after detecting the compressed liquid refrigerant.
2. Description of the Related Art
Among the functional parts constituting an air conditioner for a vehicle, an evaporator is arranged inside the vehicle (adjacent the passenger compartment), while a compressor is arranged in an engine compartment which is relatively susceptive to the influence of outside air temperature. The compressor is arranged at a position lower than the evaporator and the condenser.
Accordingly, when a vehicle parked for a long time at a place where the temperature is very low, the temperature in the passenger compartment of the car is relatively high due to sunlight shining through the vehicle windows during the day as compared to the temperature in the engine compartment as a result. That is, the refrigerant in the air conditioner moves from the warm side (evaporator side) to the cool side (compressor side) and condenses to liquid. As the compressor is arranged at the position lower than the evaporator, the condenser and so on, the liquid refrigerant collects at the compressor and accumulates in the cylinder of the compressor.
When the compressor is operated in this state, the liquid in the cylinder causes noise and rapid pressure rise which might damage the compressor. Also, with the rapid fall in engine revolutions, the performance of the vehicle suffers.
The Japanese Unexamined Patent Publication No. 191326/58 discloses a technique to solve the above problem by pulse-driving a magnetic clutch when the compressor starts and by adjusting the pulse-width of the energizing pulses so that they get wider gradually so as to increase the speed of the compressor slowly.
Also, Japanese Unexamined Patent Publications No. 146924/60 and No. 164024/60 disclose a technique to gradually engage the magnetic clutch with the aim of preventing mechanical shock when the magnetic clutch engages.
However, in the conventional techniques disclosed in the above publications, because the intermittent on/off control of the magnetic clutch is initiated not only at the time when liquid refrigerant accumulates in the cylinder of the compressor, but at any time the compressor is started, abrasion and deterioration of the magnetic clutch will occur.
Also, in the above prior arts, as idle speed is increased when there is no compressed liquid refrigerant in the compressor, the engine revolutions are further increased when the magnetic clutch is disengaged, and vibration and other problems will adversely affect vehicle performance.